(i) Field of the Invention
The present invention relates to a heating apparatus comprising a safety mechanism for interrupting energization to a heating member in an overheated state and, more particularly, to a heating apparatus suitably used as a fixing device for heating and fixing a non-fixed image on a recording medium.
(ii) Related Background Art
In a heating fixing apparatus, in order to prevent the apparatus from being damaged by an overrunning heater due to a defective temperature detection element or temperature control circuit, energization to the heater is interrupted in an overheated state. As a safety mechanism for interrupting energization to the heater in an overheated state, a temperature fuse or a thermoswitch is employed. As a countermeasure against the defective temperature fuse or thermoswitch, when an abnormal current flows through the heater, current supply to the heater is cut off.
FIG. 9 shows a circuit breaker of the heating apparatus described in Japanese Laid-Open Patent Application No. 63-49911. The circuit breaker comprises a breaking means 101 for breaking a current flowing through a heater 100, and a detection means 102 for detecting an abnormal current flowing through the heater 100 when the heater is inactive, and is controlled to break a current flowing through the heater 100 when the abnormal current is detected by the detection means 102. However, since the circuit for detecting an abnormal current, and breaking a current flowing through the heater is constituted by a large number of elements, even if one of the large number of elements malfunctions, the breaking means 101 cannot be operated in an abnormal state, and a large current is undesirably kept flowing through the heater 100.